The present invention relates to a brake actuating mechanism for a separating plate type disc brake.
With separating plate type disc brakes, one or more rotating discs having frictional linings, are forced into frictional engagement with static surfaces, by means of a pair of plate members which are arranged to separate upon rotation of one plate relative to the other. Separation may be caused by a ball and ramp mechanism, said mechanism preferably being arranged to operate with relative movement of the plates in both directions. Relative movement of the plates may be achieved by applying opposed tangential forces tot he two plates, through toggle links connected to lugs on the outer circumferences of the plates, these tangential forces being applied by an actuator which applies a pulling load to the toggle links.
With this form of brake, the frictional drag of the rotating disc on the plate may be arranged to cause further rotation of one plate relative to the other and thus produce a servo effect. This further rotation of the plates will however require rotation of the linkage mechanism and corresponding tilting movement of the pull-rod connecting the linkage mechanism to the actuating mechanism. This tilting movement of the pull-rod imposes a side load on the piston of the hydraulic actuator, which will cause scuffing on the actuator bore and will ultimately lead to failure of the piston seal. Furthermore, where the actuator includes a mechanical linkage for a hand brake, the non-linear force applied by the mechanical linkage will produce further side loads on the actuator piston.